Mobile Core i7-920XM: Power Is The Price For Better Performance

I’ve seen some crazy attempts at getting desktop-class performance onto notebooks. But there will forever be compromises, if only because there's an unbreakable relationship between speed and power consumption. Thus, when you see a 130W desktop-class Core i7 (Bloomfield) CPU shoehorned into a laptop, you don’t expect much in the way of battery life (to be fair, Thomas got nearly an hour out of Eurocom’s D900F). That’s like trying to get a V8 under the hood of a Prius—totally defeats the point, even if there is a small contingent of folks who can actually put that self-contained horsepower to use.

Nevertheless, Bloomfield was never intended for notebooks. Neither was Lynnfield. The true first-generation Nehalem-based CPU aimed at the mobile space is called Clarksfield.

Now, I say first-generation because the second-generation version is already on the calendar for January of next year. It’ll be called Arrandale and charged with fleshing out the mainstream and value-oriented segments using 32nm manufacturing and two physical cores. We’ll get into Arrandale shortly.

For now, our focus is Clarksfield, intended for the performance segment and set to replace Intel’s mobile Core 2 Extreme QX9300 and mobile Core 2 Quad Q9100/Q9000, both of which are rated at the same 45W TDP as these new Clarksfield CPUs (and below the 55W mobile Core i7 Extreme Edition).

Clarksfield: Core i7 At 45W/55W

As we heard earlier this year, Intel is no longer referring to its mobile platform as Centrino, and is instead using that designator as a reference to its wireless radios. The company plans to use Core i7, Core i5, and Core i3 as modifiers indicating a good/better/best scenario. We’re still not sold on the branding here—after all, this is exactly what we criticized Nvidia for doing in Mobile GeForce GTX Graphics: Model Inflation Gone Awry.

In essence, Clarksfield is being marketed as Core i7—Intel’s “best” mobile offerings—but with no relation to the performance you’d expect from the desktop Core i7s. And, just as Nvidia and ATI recycle specific model names (GeForce GTX 280M, Mobility Radeon HD 4870), so too is Intel invoking the popular Core i7-920 with its Core i7-920XM.

L3 Cache
Base Clock
Top Turbo Frequency
Cores / Threads
Core i7-920XM
Dual Ch. 1333 MHz
2 GHz
3.2 GHz
Core i7-820QM
Dual Ch. 1333 MHz
1.73 GHz
3.06 GHz
Core i7-720QM
Dual Ch. 1333 MHz
1.6 GHz
2.8 GHz

Of course, as you can see, there’s very little similarity between the 920XM and desktop Bloomfield-based i7-920. In fact, these mobile parts really share more in common, architecturally, with the Core i7 Lynnfield parts launched a few weeks ago. The three Core i7 Mobile CPUs are all quad-core models with 6MB/8MB L3 cache and Hyper-Threading enabled. They all boast a dual-channel memory controller supporting DDR3 modules running at up to 1,333 MT/s and 16 lanes of integrated PCI Express 2.0. The trio is armed with a much more potent Turbo Boost binning structure than Intel’s Bloomfield-based Core i7s. And the chips are being paired up to Intel’s PM55 Express chipset.

Perhaps the biggest difference is yet another new interface. Despite the similarities to Lynnfield, Core i7 Mobile CPUs drop into an mPGA 989 socket with more than twice the pin count of Core 2 Quad’s mPGA 478 interface. And whereas the desktop Bloomfield and Lynnfield chips are pinless, mobile Core i7s actually wear the pins in this relationship.

Power consumption remains fairly even. The entry-level and mid-ranged Core i7 parts (i7-820QM and i7-720QM) are 45W components, just like the mobile Core 2 Quads. Intel’s Core i7-920XM does step things up with a 55W TDP—though that’s still a far cry from the 130W desktop Core i7-920s we’ve seen used in a handful of mobile workstations.

Naturally, we’re expecting these mobile Core i7 parts to deliver threaded performance on par with we’ve already seen from Lynnfield on the desktop. The increase should be even larger in benchmarks like iTunes and WinZip (optimized for a single thread), since the flagship Core i7-920XM enjoys nine bins of Turbo Boost acceleration, running up to 3.2 GHz. With two cores active, it drops to 3.06 GHz, and with all four working, the CPU drops to 2.26 GHz.

The 1.73 GHz Core i7-820QM runs as fast as 3.06 GHz in single-threaded apps, and the 1.6 GHz Core i7-720QM clocks up to 2.8 GHz. While all three mobile Core i7s include Hyper-Threading, giving away their intended desktop replacement purpose, only the top two SKUs feature an 8MB L3 cache. The entry-level model is limited to 6MB.

Create a new thread in the UK Article comments forum about this subject
This thread is closed for comments
Comment from the forums